1. Field of Invention
This invention relates to a cylindrical pin tumbler lock taking a flat key and having spring biased split pin tumblers embodying false segments and a pair of spaced shear lines required to be cleared.
2. Description of the Previous Art
Cylindrical locks embodying axially aligned rotatable members having pin tumblers are known in the art. Various efforts have been made to develop lock structures resistant to picking or manipulation. Improvement is present in the instant structure in providing false tumblers permitting just sufficient rotational movement therein to misalign the tumbler bores and having two spaced shear lines to be cleared by the tumblers in order to unlock the lock.
An example of the prior art is present in U.S. Pat. No. 541,630 to Ridgway in which a pin lock is disclosed in which a guard is disposed between stationary and movable surfaces in having divided pin tumblers whereby the guard deceives a lock picker.
In U.S. Pat. No. 3,885,409 to Genakis, a pin tumbler lock is disclosed in which a cylinder has a plug or sleeve surrounded by bands or rings, a key way in the plug has top and bottom pins in pinways, each bottom pin has a ball for contact by a key, an attempted pick of the lock offsets the rings to a degree that the lock is inoperable.
The present invention provides substantial improvement in making a lock pickproof.